The lawmakers drew a comparison between the actions they saythe EPA has taken with the Internal Revenue Service, which isembroiled in controversy over its targeting of conservativegroups for extra scrutiny.

Republican Senators David Vitter of Louisiana, CharlesGrassley of Iowa and James Inhofe of Oklahoma, andRepresentative Darrell Issa of California, raised the issue in aletter to the acting administrator of the EPA.

The four lawmakers serve as the top Republicans on theenvironment, judiciary and House oversight and government reformcommittees, respectively.

They asked why 92 percent of Freedom of Information Act(FOIA) fee waivers were granted to "environmental allies," whilejust 8 percent were granted to conservative think tanks. Thedisparity came to light this week in a report by a conservativeresearch group.

Agencies can waive fees for requested information if theydetermine the information contributes to the publicunderstanding of governmental activities.

"This disparate treatment is unacceptable, especially inlight of the recent controversy over abusive tactics at theInternal Revenue Service, which singled out conservative groupsfor special scrutiny," the lawmakers wrote in a letter to BobPerciasepe, the EPA's acting administrator.

The Republicans accused the EPA of colluding with groupsthat share its political agenda and requested that the agencytakes steps to ensure this does not happen again.

They requested that the EPA provide a list of all fee waiverdecision letters on a monthly basis, make the agency's FOIAofficer available for a transcribed interview and provide anymaterials used to train FOIA officers on how to process feewaiver requests.

Vitter met with Perciasepe earlier in the week and said hemade progress with him on five key areas in which the EPA canimprove its transparency, including how it handles FOIArequests.

Interest groups, researchers and journalists have filed FOIArequests with the EPA to understand how it goes about itsprocess of writing regulations. Conservative groups have calledthis process opaque.

Perciasepe is heading the EPA while President Barack Obama'snominee to head the agency, Gina McCarthy, remains in the middleof a tough confirmation process.

McCarthy has had requests to answer more than 1,000questions by Republicans on the Senate Environment and PublicWorks Committee, which Democrats have termed a record number.

Her nomination was sent to the full Senate on Thursday aftera party line vote in committee. No date has been set forconsideration. The first committee vote scheduled on McCarthywas abandoned when Republicans boycotted the meeting.